Basic principles for interferometry with ultrashort-pulse lasers are described. Different interferometer configurations for use as sensors for optical shape and deformation measurement are discussed. The sensor configurations that are mainly treated, are: the non-scanning white-light interferometer as distance and pulse length sensor. Speckle interferometry with ultrashort pulses for three-dimensional shape measurement. Light-in-flight recording by holography for visualization of light propagation and for three-dimensional shape measurement. Digital light-in-flight recording by holography. Holographic interferometry with ultrashort pulses.

The influence of the speckle size to the measurement accuracy is investigated by discussing the spatial frequency distribution of the signal of specklegrams on the Fourier domain with the results of experiments and computer simulations. It is found out that the relationship of the location between the distribution of noise element and of signal element of fringe images in the spatial frequency domain is related to the measurement accuracy. From these discussions, we would conclude as follows: the measurement accuracy is decreased, because the noise element in the specklegram increases when the speckle size is bigger than the size of the pixel of the CCD. On the other hand, there are many speckles in single pixel of the CCD in the case that the speckle size is smaller than the size of the pixel. Consequently, because the output of each pixel of the CCD is averaged with the intensity of each speckle in one pixel, this averaging effect of the intensities of speckles would bring the decrease of the measuring accuracy. The results show that the measurement accuracy of this method is maximized in the case that the speckle size is as large as the pixel size of the CCD.

We are currently introducing a new scanning triangulation method for absolute 3D profiling of a macroscopic scene based on fringe projection technique. A scanning focal plane allows the phase to be determined for any desired depth range of the measurement volume. Furthermore, the limitations of the depth of focus occurring by projected light techniques will be overcome, allowing a large aperture and therefore better use of light. Two different systems based on this technique will be shown: System I uses both vertical and lateral translation of a Ronchi grating. System II uses an LCD element for generation of different fringes which has to be translated vertically, only. The basic principle of the new method is explained. First measurement results of both systems demonstrate the efficiency of the newly developed algorithms and the innovative measurement arrangements.

Local material insufficiencies on or near the object surface lead to locally high dense fringes at the displacement and shape measurement by holographic interferometry and TV- holography. In such case cutting out fringes results in relatively easy interpretation of the remaining interference pattern and identification of the defect. Fringe compensation techniques are widely used for eliminating the background fringes. The paper proposes a compensating technique based on phase-shifted interferograms. Its principles and applications are presented.

The principles of operation and optomechanical design of novel optical extensometer OPEX for tensile testing machines is presented. The system provider on-line strain measurements performed at an arbitrary measurement base. OPEX is integrated with a tensile loading machine so it can be used for active controlling of the machine setup. The applicability of the system is demonstrated by determination of elongation of various mechanical samples subjected to uniaxial tensile tests.

The quality of interferometric measurement methods, such as fault detection by shearography, is highly influenced by the intensity distribution of the illuminating light. Usually it is intended to obtain a homogeneous object illumination while common laser light sources provide a Gaussian intensity distribution. In this paper it is investigated how the intensity distribution of the detected light is influenced by the polarization states of the incident and the scattered light. In literature usually the Stratton-Chu equation is used to describe depolarization effects. However, this equation is valid only in the Fraunhofer region, which is unsuitable for most interferometric measurements. For this reason a still unpublished general expression for the amplitude of the electromagnetic field close to the scattering surface is derived. Based on this novel formula the correlation between the intensity distribution and the polarization state of the scattered light is investigated analytically, numerically and experimentally. In the numerical part the integral formula is used to generate the light field scattered by a metal plate. As input data for the simulation the measured surface structure of a real metal plate is used. Additionally, the theoretical results are compared to measured intensity distributions for several combinations of input and output polarization states.

Point clusters of measured shapes achieved with the digital light-in-flight recording by holography method, is combined with CAD - Computer Aided Design software to obtain convertible formats for design and simulation software. The point cloud is constructed to a b-spline surface by least square fitting. The b-spline surface is converted into IGES- format in order to be readable for CAD and other software. A simple deformation experiment is made which demonstrates the advantages of combining holographic measurements with FEA- analyzes in order to adjust the constraints, the boundary conditions and loads in the simulation model to better fit experimental results.

Due to finite width of a spectral line, the visibility of the more fringes, formed by a grating and the image of another similar grating, produced by self-imaging technique, reduces by the increase of the image order. This effect has been exploited to specify the line shape, by taking Fourier transform from the visibility curve of the more fringes. The technique also renders to specify the non symmetric spectral line shapes, which are very difficult to determine by interferometric techniques. When a dispersive material, liquid or solid, is held between the gratings the visibility curve changes. It is shown that by comparing the Fourier transforms of the visibility curves obtained with and without sample, the dispersion function of the latter can be specified.

For measuring the 3D shape of complex objects by optical methods the optical sensor or the object have to be moved into multiple, overlapping measuring positions so as to view the entire surface. The resulting point clouds taken from the different views then have to be merged into a common coordinate system to obtain the final complete 3D view. Here we propose concepts of 3D-measurement arrangements using structured-light illumination with a digital-light projection unit to obtain a full-body view within a self- calibrating measurement strategy, whereas the necessary merging of the single views takes place fully automatically and done without any marker on the object surface, objects features, other merging procedure or high accurate object/sensor handling system. On the basis of this strategy different mobile and stationary arrangements are proposed and realized. A first integration in an industrial process will be presented showing the power of this concept by measuring the complete 3D shape of automotive parts and design objects within volume of 1dm³ up to 1m³. The measurements with this system showed a coordinate measurement accuracy of up to 10^-5 of the field size.

This paper describes a new triangulation-based laser rangefinder for measuring the 3D shapes of objects with hybrid reflectance, which combines Lambertian reflectance and specular reflectance. To date, ordinary laser range finding techniques have rarely been used to measure objects with hybrid reflectance. Like ordinary rangefinders, the proposed rangefinder consists of a light-stripe generator, a lens system, and an image sensor. The core of the scheme of our rangefinder is the lens system, which consists of a field stop, a lens, and shield masks. The basic concept of the proposed rangefinder is to maintain a constant incident angle of a light-stripe upon the image sensor by using a shield masks, resulting in the ability to play a triangulation system to the measurement of objects with specular reflectance. We designed and built a prototype rangefinder. The experimental results demonstrate that the proposed rangefinder allows the measurement of hybrid objects with almost the same level of accuracy as that of Lambertian objects and specular objects. The proposed rangefinder is especially valuable for industrial purposes, since consistent accuracy and high reliability are assured even for objects with unknown reflectance properties.

This paper discuses an apparatus used in industrial inspection for optically detecting dimensions. In particular, the configuration of optical unit with compact in size and simpler in construction, and signal processing unit with resolution to be better than 0.1 micrometers are described. The key devices of the new optical unit are optical scale and light source. The optical scale consists of one moving and two stationary gratings. Both of these gratings have different pitch lengths. For example, the pitch of the moving and stationary gratings are 50 micrometers and 10 micrometers , respectively. These pitches are set to odd integer multiples. The optical scale, directly irradiated by a divergent light emitted from a laser diode, generates two sinusoidal signals with a 10 micrometers period. By using the divergent light, the need for a collimating lens is eliminated. This reduces the overall size of the optical unit. The signal processing unit operates on the two signals for detecting the signal phase at the stop position of the moving grating. The basis of this phase detection is a simpler linear operation. By using the linear operation, high resolution detection of the signal phase is accomplished by segmenting an interval of one cycle period of the signal into more than 300 parts.

Laser-Doppler Velocimetry is a contact less method for measuring the speed and the path length of moving solid- state surfaces or of fluid streams. In the past the main application of this method was fluid mechanics. No other method was as suitable as Laser-Doppler Anemometry to measure the speed the streams at arbitrary positions. Therefore the market accepted the very high price of these systems. In the past for the measurement of solid-state surfaces mostly other methods with a more reasonable price were used. However from a pure technical point of view a contact less and precise method as Laser-Doppler Velocimetry is also very attractive for the measurement of solid-state surfaces. The method is suitable for nearly any type of technical surface. The measurement procedure does not damage the surfaces and no slippage occurs. These advantages will be become important also for standard applications, if the price of the LDV systems can compete with the price of other methods.

The stringent figure requirements for optics used in Extreme UV (EUV) projection systems pose a significant challenge to metrologists. The large asphericities combined with low RMS figure error tolerances require novel measurement techniques. Such a method to measure absolute optical path differences (OPD) with 0.1 nm accuracy over ranges of several millimeters is presented. The method combines two different measurement techniques: frequency modulation to determine the absolute OPD with an accuracy of half a wavelength and heterodyning to determine the OPD modulo one wavelength with an accuracy of 0.1 nm. By combining the results of the two methods, the absolute OPD is determined with the large range of the frequency modulation and the high accuracy of the heterodyning. Measurement results for the heterodyning method are presented. In addition, a method to dynamically characterize the frequency behavior of a sweeping tunable external cavity diode laser is shown.

This paper presents research results on the relationships between surface roughness and lightness of the surfaces machined by polishing, grinding, turning, and milling. The objective of this study is to investigate the correlation between surface roughness heights and lightness values measured on various material surfaces machined by the four processes. This may provide a fast and cost effective method for surface texture characterization. The four processes were chosen based on their distinct differences in the surface roughness values they produce. Some linear relationships were obtained for the surface roughness and lightness values.

Range finders have been widely applied to measure distances and shape along a single line. In combination with a displacement device, ranger finders can be used to scan several lines of a surface and, by numerical reconstruction, recover the surface's shape. A three-line range finder was developed in order to permit the measurement of position, spatial orientation and local curvature with a single shot. That configuration can make the measurement process faster and allows curvature measurement of movable parts. The three-line range finder was designed to be mounted on a robot arm. The spatial coordinates and orientation of the range finder are determined by the position and orientation of the robot arm. A coordinate transformation is applied to the local measured data in order to compute the global values of those parameters. As a result, the global values of those parameters. As a result, the global coordinates, normal vector and curvature of several points over a free form surface are known. The numerical reconstruction of a free form surface becomes easier a more accurate if more elaborated information is available about the unknown surface. The size of the cloud of points can be significantly smaller. The paper also presents preliminary results of the overall performance of the developed system.

The concept, optomechanical design and principles of operation of novel laser grating interferometer are described. The system works in on-line, local strain measurement mode and off-line full-field, in-plane displacement/strain measurement mode. The extensometer is fully automatic and integrated with standard loading machine. Its applicability for solving various experimental mechanics and industrial problems is shown at numerous examples.

A plastic disk for the next generation of a hard disk requires high quality surface. Especially its flatness is very important. A plastic disk inspection system is proposed by using a 2D birefringence distribution. Small birefringence is a serious problem that is caused by internal strain or residual stress in disks. It is necessary for the birefringence measurement to determine the relative retardation and the azimuthal angle of the fast axis in plastic disks. A 2D birefringence distribution is measured in this system. Several images captured by a CCD camera are sufficient for one birefringence distribution analysis. These experimental procedures and the results of plastic disks for hard disks are discussed.

Laser interferometric methods opened the way to measure displacements and deformations of an object in a while- field, non-contact and 3D manner. Therefore, they are used in non-destructive testing and validation of 3D finite element (FE) simulation results. This paper emphasizes the fact that the process of validating an FE result comprises in turn the validation and assessment of the optical measurement method and the experimental bou8ndary condition. Application examples for FE analysis validation and NDT from machine engineering, space technology, and biomedical engineering are presented.

The method of endoscopic electronic-speckle-pattern interferometry (ESPI) is a tool for detection and visualization of deformations and movements in technical cavities as well as for non-destructive minimal invasive diagnostics within body cavities. Here, a spacial phase shifting (SPS) method is chosen for additional setup and the investigated specimen in comparison to temporal phase shifting techniques. With a simple arrangement, the SPS technique is adapted to the special conditions of standard endoscopic optical imaging. The characterization and optimization of the interferometer is carried out on technical specimen. To demonstrate possible applications of endoscopic ESPI and spatial phase shifting endoscopic (ESPI) on biological tissues, non-destructive investigations of biological heart valve prostheses are performed. The quality of the obtained phase difference fringes is sufficient for phase unwrapping and for visualization as well as quantitative evaluation. In conclusion, the results of the investigations show that it is possible to detect structural differences in tissues underneath the visible surface by application of SPS endoscopic ESPI even of biological specimen with a wet and low reflecting surface.

In structural testing the determination of the dynamic structure response is one of the most important and difficult tasks. Double pulse holography interferometer has been widely used for analysis of the dynamic behavior of the structures. Recently PulsESPI techniques are increasingly used to replace conventional double pulse holography interferometer, not only taking over the main benefits of holography towards conventional measuring techniques, such as full field, non contact and sensitive, but also uses modern video and computer techniques for image capturing and processing. Recent developments have extended the capabilities of PulsESPI techniques to 3D measurement of dynamic structure response and modal analysis of vibrations.

The dynamic speckle is a phenomenon generated by laser light scattering in biological tissues and it is also present in some industrial processes where the surfaces exhibit some kind of activity. In our case, the process of drying of paint has been studied and its activity is explored using dynamic speckle techniques. Two alternative speckle contrast methods are presented to characterize faster processes.

Micro-optical components such as microlenses and microlens arrays are of growing interest in the fields of laser beam shaping, optical processing and similar applications. The characterization of these components require a fast and robust measurement technique, especially for simultaneous inspection of lenses manufactured in array structures e.g. on silicon wafers.

This paper describes a grating projection method for the measurement of surface profiles of objects. In this kind of profilometry, a grating with binary transmittance distribution has been utilized usually. And in these cases such a problem is known as an error is caused due to the non-sinusoidal transmittance distribution of the grating. And another difficulty is also indicated that shifting of the grating is given by mechanical movement of the grating. Here we propose to use a hybrid grating is given by mechanical movement of the grating. Here we propose to us a hybrid grating which consists of a conventional binary grating and a liquid crystal binary grating. Then moire pattern is produced by superposing these two binary gratings. When two binary gratings are overlapped with an appropriate gap, the resultant more pattern becomes closely sinusoidal in intensity distribution. The, in the optical arrangement for profile measurement using this hybrid grating, when the LC gratin pattern is moved, the projected pattern is shifted arbitrarily in phase. Surface profiles of some samples are measured to show validity of the more pattern projection and utility of the prototype system.

Fringe Projection systems generate phase distributions of an object illuminated with a specific fringe pattern. These phase correspond to the object coordinates. It is mostly necessary to transform the dimension-less phases to a metric dimension. Until today this is realized by photogrammetric techniques, which are subdivided into three main processes. At first a reference plane is defined. Then a grid within this plane is fixed. In the third step, the height axis is calibrated by different methods, for example, by use of a single height step or another well defined base object. This article describes a new method to calibrate the measuring volume by a multi-value calibration algorithm. As a first step, the fringe projection systems detects the phase distribution of a plane, denoted as reference plane. The, the plane moves stepwise in z-direction. In each step the phase distribution is detected, while an interferometer measures the distance of the z-coordinate form the reference plane. Together with the discrete x-y-coordinates of a CCD- detection unit, a 3D measuring volume is defined. The volume calibration is performed by separate polynomials for each x- y-coordinate, which are derived from the corresponding values of the phase distributions and the interferometric height values. With this method some problems of the conventional 'single value calibration' can be solved. This contribution describes the theoretical solution of the problem and presents first experimental results.

Shearography is a full-field optical technique usually used for the determination of surface strain. Interferometric speckle patterns recorded before and after object deformation are correlated to obtain the displacement gradient. Further calculation yields the surface strain. Ful surface strain measurement of displacement derivative from a minimum of three illumination, or viewing, directions. Shearography can also be used to measure surface slope and shape by recording interferometric speckle patterns before and after displacement of the optical source. For a curved object the object shape introduces errors into the displacement gradient measurement, resulting from the variation in the sensitivity vector across the object surface, and from the dependence of the applied shear upon the surface slope. In this paper the surface slope of a gas main pipe, of diameter 90 mm, is measured using a source displacement technique in shearography. The surface slope is then integrated in the shear direction to yield the surface shape. The displacement gradient is measured using three illumination directions and a single viewing direction. The displacement gradient measurements are corrected for errors due to the object shape and mapped onto the surface of the object.

We present a novel interferometric method for testing refractive conical lenses. The optical configuration requires only two mutually coherent plane wave fronts transmitted through the optical component under test. It can be interpreted as reversal shear interferometric technique. The method can also be considered as an interferometric fringe projection method. Measurements have been realized for determining the base angle of the refractive cone under test and the aberrations introduced.

The spectral interference of two beams form a white-light source, a tungsten halogen lamp, is measured at the output of a dispersive Michelson interferometer by a low-resolution miniature fiber optic spectrometer when the interferometer beam splitter is made of fused silica. It is confirmed that the spectral interference fringes are resolved only in the vicinity of the equalization wavelength whose value is dependent on the group optical path difference in the interferometer. Thus, the equalization wavelength is measured as a function of the displacement in the interferometer in the spectral range approximately from 490 to 870 nm. Moreover, when the group refractive index of fused silica is evaluated at the equalization wavelengths by using the Sellmeier dispersion equation, it is confirmed, in accordance with the theory, that the measured displacement as a function of the group refractive index of fused silica is a straight line whose slope gives the effective thickness of the beam splitter. It is also revealed that when the effective thickness of the beam splitter made of fused silica is know with a sufficiently high accuracy, the differential group refractive index of fused silica in a spectral range from 490 to 870 nm can be obtained from the measurement of the equalization wavelength as a function of the displacement in the interferometer.

It is known, that phase dislocations in objective speckle fields can be found at regions where the intensity of the wave-field disappears. In interferograms, created by object I've speckle fields, those dislocations usually form dipoles. They arise when the position of the dislocations changes between two object state. In this paper it is shown, that phase dislocations in interferograms from subjective speckle fields also form dipoles. They produce a noise- amplitude on the corresponding phase-map, which makes unwrapping more difficult. The mean width and the number of theses dipoles are investigated in dependence of the correlation and the density of the corresponding subjective speckle field. All these results have been obtained experimentally and have been additionally proofed by means of simulations. Because dipoles on the phase map appear at regions, where the corresponding intensity disappears, a modified line-scan-algorithm is proposed which only takes the bright areas into consideration.

We provide a simple solution for the particular problem of the in-service inspection of aeronautic surfaces in order to detect bumps that otherwise it is made visually and usually less reliably. Bumps and other surface defects can be a symptom of a more serious internal damage. We have extended the use of the well know shadow Moire technique to be implemented in convex curved surfaces. The use of flexible Ronchi grating allows its adaptation to a convex general surface. The effect is the contrast enhancement of only the small defects sweeping-off other misleading height profile fringes. The result obtained are quite satisfactory compared to the use of flat reference gratings. The experimental set- up consists of a plastic foil with a printed Ronchi grating stretched between three points which adapts to nay cylindrical or conical convex surface independently of the relative grating-surface orientation. Static quantification of defects profiles is also possible by means of with an attached CCD camera. Visual detectability of local surface structures lye in the range of approximately 30 micrometers in depth.

Analysis of noisy interferometric signals and distorted interference fringe patterns with complicated structure is very important for solving problems of metrology and nondestructive testing. New nonlinear fringe processing method with spatially dependent filter impulse response is investigated. Unlike conventional filtering methods, in this method a filter impulse response is formed by the local empirical histogram modification with the spatial weighting function inside a dimensionally varied area dependent on the local fringe intensity distribution. High noise-immunity of the method proposed was verified experimentally when processing real noisy distorted fringe patterns.

Parameters affecting the sensitivity of a 3D measurement system using the phase shifting technique were investigated. A simple wedge object was used for the experiments to study the factors without the possible complication caused by using a complex object. A calibration procedure was derived to investigate to what extend the important parameters affected the results of the depth measurement by the use of the phase shifting method. These parameters were the pitch, projector magnification, camera magnification, and projection angle. The results of the experiments are presented and possible reasons for such results are discussed in this paper.

The method and circuit, which are presented in this note, offer the original solution for the extraction of a laser spot or trace from the intensity range images, using a simple hardware and software. Its advantages over existing profilers are numerous, and include the exclusion of frame- grabbers, flash A/D converters, strong processors, large memory requirements, mechanical parts and complex software algorithms.

An optical method for measurement of static deformations is presented. This non-contact technique is based on interference of the light and the principle of phase shifting. The theory of phase shifting interferometry is shortly described and there are given four possible multistep algorithms for evaluation of the phase difference of the interference field induced by a static deformation. It is shown a new way how to evaluate the phase difference of the interference wave field, which is closely related to deformations of tested objects. The main part of this paper deals with an analysis of proposed algorithms. The experimental system, which is applied in static deformation measurement and which can be easy modified for industrial applications, is described and the method is demonstrated on an example.

A novel method for measurement of angular displacement in one or two dimensions for arbitrarily shaped objects is presented. The method is based on Fourier transforming the scattered field form a single beam that illuminates the target. The angular distribution of the light field at the target is linearly mapped onto an array image sensor placed in the Fourier plane. Measuring this displacement facilitates the determination of the angular displacement. It is demonstrated both theoretically and experimentally that angular displacement sensor is insensitive to object shape target distance and any longitudinal or transverse movement of the target, if the image sensor is placed in the Fourier plane. A straightforward procedure to place the image sensor in the Fourier plane is presented here. Theoretically and experimentally, it is shown that the method has a resolution of 0,3 mdeg for small angular displacement and methods for further improvements in resolution are discussed. No special surface treatment for surfaces having irregularities of the order of or larger than the wavelength of the incident light. It is shown that this is the case for most surfaces of practical interest. Furthermore it is shown that robust, non contact optical systems for industrial applications can be produced.

Optical tomography system utilizing two laser diode module lasing at 685 nm and 785 nm wavelengths is presented. During one scanning procedure about 8000 electronic transmission images of optically nonhomogeneous object are registered by us of CCD camera. Special prepared software based on modified Radon transform is applied in order to reconstruct of 3D structure of the object. Some examples of advantages of two-wavelength system in comparison with other systems are presented as well. As conclusions some specific industrial applications of the two-wavelength optical tomography system are discussed.